Method and apparatus for purifying wet steam



Jar 5, 1937. I E. M. FRANKEL METHOD AND APIAIiATUS FOR PURIFYING WETSTEAM Filed Dec. 7, ,1935 2 Sheets-Sheet l |NVENTOR [DIM/f0 /7 fawn 1ATTORNEY 5, 1937. E. M. FRANKEL METHOD AND APPARATUS FOR PURIFYING WETSTEAM 1935 2 Sheets-Sheet 2 Filed Dec. 7

lam v INVENTOR ATTOFKNEY Patented .Fan. 5, 1937 WET STE

Edward M. Frankel, New York, N. Y.

Application December 7, 1935, Serial No. 53,318

7 Claims.

My present invention relates to improvements in methods and apparatusfor purifying wet steam. Steam as it leaves the steam releasing drum ofthe boiler offers a problem in purification chiefly for two reasons: (1)because it ontrains droplets of relatively impure water especially thatcollecting in the steam releasing drum which often has a distillatesolid content of 3,000 or more parts per million and, (2) because ofentrained solid matter picked up from the foam or other material on thesurface of the water in the drum. Wet steam thus obtained is commonlypassed through mechanical separators which remove a large portionalthough not all of the entrained droplets and rather little of theentrained solid matter. When the steam is superheated, dropletsremaining are vaporizedand the residue which they yield upon evaporationis thus added to the solid matter entrained by the steam when it enteredthe superheater. The foreign matter thus entrained in the superheatedsteam exerts a cumulative deleterous effect upon the various apparatusin which the steam is utilized particularly upon the blades and guidepassages of the steam turbines.

It has been proposed to wash the steam with waterof greater purity thanthat entrained in the steam. This washing is partially effective in thatit removes the solid materials and some of the impurities carried by theentrained water. As heretofore proposed, it is only partially effectivehowever, because the wash water itself becomes contaminated by thematerials washed out and is itself entrained in the steam so that whilethe steam is partially purified, it is not fully so by such previouslyproposed treatments and the amount of impurities left in the steam issuflicient to adversely affect the steam utilizing apparatus.

My present invention seeks to overcome the drawbacks mentioned first byproviding for an improved more or less automatically regulatable supplyof distilled water for washing and further by providing for an improvedmethod and means of washing and subsequent purification treatment of thesteam. Further according to my invention, this supply of distilled wateris obtained by passing the steam through a condenser in which'the steamis used to heat the feed water and is thereby condensed to give adistillate of great purity since the steam has been previously washedbefore being admitted to the condenser. The distillate obtained is thenpassed to the washer. In this manner a supply of pure distilled water isobtainedwithout the sacrifice of boiler efiiciency since heat lost bythe steam is acquired by the feed water which, moreover, being at atemperature more nearly that of the water within the boiler creates lessdisturbance when admitted thereto. By my improved system of washing inwhich a countercurrent of wash water to steam is set up, the steam iswashed free of entrained solid particles while any particles of waterultimately entrained by the steam are composed almost entirely of freshdistillate. Then by leading the wet steam over a series of condensertubes, also preferably arranged to give a countercurrent flow ofsteam tocooling (feed) water, further purification and substantial eliminationof the then entrained distillate occur since one action of thecondensertubes is to provide focal points upon which the water particlescollect .and

coalesce. Droplets remaining in the steam leaving the separator are ofsuch purity as when evaporated in the superheater, leave but anegligible trace of solid matter.

It is desirable thatmeans be provided for insuring'the proper flow ofwash water from the washer, and for this purpose I have provided animproved arrangement of partswhereby the used wash water is removed bybeing inspirated into the stream of boiler feed water leaving thepurifier.

Further objects of the invention and the advantages thereof will beevident as the description proceeds and the features of novelty will bepointed out in the claims. For a full understanding of the invention,reference may now be had to the drawings in which Fig. 1 shows anillustrative embodiment of my invention in conjunction with a water tubeboiler.

Fig. 2 shows the improved device in longitudinal section, the same beingtaken on line 2-2 of Fig. 3.

Fig. 3 shows the device in vertical cross section taken on line 3-3 ofFig. 2.

Fig. 4 is an enlarged detailed view partly in section taken along line4-4 of Fig. 3.

Referring to Fig. 1, wet steam from the drum l0 leaves the boilerthrough pipe II and passes through branch pipes l3 and M to the purifierdenoted generally by l2. The steam leaves the purifier by means of pipeI6 through which it passes to the superheater H. The superheated steamleaves through pipe l8 and passes therethrough to a prime mover I9. Thefeed water enters the system through the purifier l2 being admittedthereto by pipe 2| and leaving through pipe 22 by means of which it isconveyed to drum III of the boiler.

Referring now to Figures 2, 3, and 4 showing details of construction ofthe purifier, the shell 25 thereof desirably of cylindrical shape isdivided by partitions 26, 26 into an upper compartment in which islocated condenser A and into a lower compartment in which is located thewasher B. The washer consists preferably of a plurality of wash chambersin cascade i. e. a, b, c, d and a, b, c, 11' formed by verticallyextending partitions 28, 29, 30 on one side and 28', 29' and 30' on theother side, the number of partitions and of chambers formed therebybeing susceptible to variation. In order to fix the water level in eachchamber the same are each provided with a plurality of educt pipes 3|(Figs. 3 and 4) which lead from the position of the water level of onechamber to the adjacent bottom of the next adjoining chamber in thedirection of water flow. The wash water is removed from the system inthe lowermost chambers 32, 32 by. means of educt pipes 33 at spacedintervals (see Fig. 2) which pipes terminate in a collector pipe 34, asimilar arrangement of educt pipes 33 and a collector 34 being providedfor the right hand side of the device as seen in Fig. 3. As shown, thepartitions 26 each have a downwardly extending portion 26a which providea central well for liquid through the device and also serve as baiiiesfor the steam. Other baflies depend from the partitions 26 to beneaththe water level of their respective chambers and are indicated at 3! to39 and 31' to 39'.

Bafiles 31 to 39 and 31' to 39' preferably are provided with pear shapedopenings 40, Fig. 4

which are normally below the liquid level, such openings facilitatingpassage of the steam through the washer and making for a constantvelocity thereof at all ratings.

The condenser is formed preferably of tubes 45 which extend from aheader 46 at the left of Fig. 2 to header 41 at the right thereof. Thespace between the header 46 and the end 48 of the shell is preferablydivided into chambers by partitions 49 and 50 while the correspondingspace enclosed by the opposite shell end 5| is divided by partition 52.This arrangement causes the water to make a plurality of passes, in thiscase three, through the condenser counter current to the passage of thesteam whereby the hottest steam first contacts with the hottest tubes.The heated water is finally collected in the space 54 and passes outthrough a pair of outlets 55, 55 (see also Fig. 1), such outlets beingdisposed opposite the ends of pipes 34 and 34 respectively in such amanner as to form an ejector with the ends of the feed pipes and thuscarry out of the washer the condensate collected by said pipes.

The condenser is also provided preferably with steam bailies 51, 58, 58'and 59 so as to aid-circulation of the steam over the tubes, the steamfinally leaving the device through outlet 66. The impure steam entersthe device through the distributer pipes 62, 62, such pipes joiningcompartments 32 and 32' by a plurality of nipples 63 spacedlongitudinally of the device, Figs. 2 and 3.

In the operation of my improved device, the wet impure steam from theboiler drum [0 is caused to enter the washer through the distributer 62,62 and the nipples 63, one part passing through the wash chambers d to ain series and the other part through chambers 11' to a in series, thestreams uniting in the central well and thence passing through the vaporspace of the condenser. In traversing the wash compartments steam iscaused to pass beneath the wash water through the pear shaped openings40 whose shape causes greater area of passage as the volume of steam isincreased. In passing thus from one chamber to the next the droplets ofentrained water from the boiler are replaced by the water in the severalcompartments. However, since the water in these compartments issuccessively purer, the steam emerging from the compartment a, a willhave entrained in it only droplets of substantially pure distillate.Also the entrained solid particles are completely removed. The steam nowpasses through the vapor space of the condenser A wherein the steamfirst impinges upon the hottest tubes 45 which are wet with condensateand which cause the droplets of already substantially pure water tocoalesce and to be replaced with those of even greater purity as thesteam ascends through vapor space. Finally the completely purified steamcontaining some moisture passes out of the device through the opening 60and thence into the pipe I 6 by means of which it is conveyed tosuperheater H as already mentioned.

The condensate which forms on the tubes 45 is caused to collect in thewell formed by the members 26a and flows therefrom through the eductpipes 3| successively through the compartments a, b, c, d, on one sideand a, b, c, and d on the other side acquiring more and more impuritiesfrom the steam until finally it reaches the chambers d and d and leavesthe system through the pipes 34 and 34' by uniting with the heated feedwater as previously described. The mixture of feed and wash water is nowpassed to the boiler through pipe 22.

If desired, the wash water can be kept separate from the feed water andanother disposition made of it using a modified arrangement not shown.

One important advantage of my invention is that the amount of condensatefurnished for washing purposes varies substantially automatically withthe amount of steam produced since if the boiler is operated at excessrating for example, the amount of feed water will be proportionatelygreater, a greater quantity of heat will be exchanged and hence agreater quantity of condensate will be produced. 0n the other hand, whenthe boiler is operated at less than the full rating, the reversesituation will occur and a correspondingly smaller quan tity ofcondensate will be produced. The water fed to the boiler may bepreheated in the usual economizers or other heat saving devices as inordinary practice, such further heating as occurs in the purifierserving to bring the feed water to more nearly the boiler temperature.This is an advantage especially in modern high pressure practice wherethe metal parts are made extremely heavy and equalization of temperatureamong difierent parts is correspondingly made more diflicult. The hotterfeed water accordingly produces less shock and sets up fewer strains inthe boiler.

It will be understood that various changes may be made in the describedembodiment without departing from the spirit of my invention or thescope of the appended claims. For example, if desired, only a portionrather than all of the boiler feed may be passed through the purifierand the remaining portion passed to the boiler directly.

I claim:

1. The method of purifying wet steam and of boiler operation whichconsists in first washing the steam, then condensing a portion of sameto form a condensate by passing said steam in indirect thermal contactwith the boiler feed water, then using said distillate as the washingmedium in said washing step and feeding the thus heated boiler feedwater to the boiler.

2. The method of purifying wet steam and of boiler operation whichconsists in first washing the steam, then condensing a portion of sameto form a condensate by passing said steam in indirect thermal contactwith the boiler feed water, then using said distillate as the washingmedium in said washing step, and passing the thus heated boiler feedwater and the washing medium to the boiler.

3. In a device for purifying wet steam, in combination, a washer for thesteam and a surface condenser, means for passing the boiler feed waterthroughsaid condenser, means for passing the steam to be purified firstthrough the washer and then through the condenser, means for passing thecondensate from said condenser to said washer and means for adding theused wash water to the feed water which has passed through the condenserby causing saidwash water to be inspirated by a stream of said feedwater.

4. In a device for purifying wet steam, a horizontally disposed cylinderlongitudinally divided into an upper condensing compartment and a lowerwashing compartment, means for passing steam to be purified through thewashing compartment and then through the condenser compartment, meansfor collecting the condensate formed and passing it through the washerin countercurrent to the flow of steam, means for a dividing said washerinto compartments. a

plurality of longitudinally spaced eduction pipes in said compartmentsdetermining the water level therein and a plurality of longitudinallyspaced eduction pipes for withdrawing the'water from said washingcompartment.

5. The method of purifying wet steam prior to using the same for poweror heating purposes, which consists in passing the steam from the boilerto a washing zone and there washing same with a washing medium, passingthe washed steam directly to a condensing zone, there condensing aportion of said steam to form a condensate by passing same in indirectthermal contact with water of appreciably lower temperature, thenpassing the condensate so formed to the washing zone to constitute saidwashing medium, and then passing the washed steam. from said purifyingsystem.

6. In a steam purifying system adapted to receive steam of relativelylow purity from a boiler and deliver steam of relatively high purity toa superheater in combination with said boiler, a washer having meansproviding a liquid and vapor contact, a surface condenser includingmeans for passing a cooling fiuid therethrough, means for conducting thewashed steam directly to said condenser, whereby to condense a portionof same, and means for feeding the condensate so formed to said washerto constitute the washing medium therein.

7. In a steam purifying system adapted to receive steam of relativelylow purity from a boiler and deliver steam of relatively high purity toa superheater in combination with said boiler, a washer having meansproviding a liquid and vapor contact, a surface condenser includingmeans for passing a cooling fluid therethrough, means for conducting thewashed steam directly to said condenser, whereby to condense a portionof same, means for feeding the condensate

